Justin Teilhet didn't know what happened as he and his wife, Becky, couple hiked beneath storm clouds and across the high, stunning vistas of Rocky Mountain National Park on Friday. He just knew something was wrong.

"We were hiking in the mountains one minute, and the next minute I couldn't stand up," Teilhet, 41, recalled days later.

In that minute, a lightning bolt surged to the ground, killing Teilhet's wife of nearly 22 years and knocking Teilhet and a family friend instantly to the ground. The three were hiking that afternoon along Trail Ridge Road, one of the highest and most exposed mountain roads in the country, when a seasonal Colorado thunderstorm turned a scenic stopover into a deadly encounter.

Becky Teilhet, 42, of Yellow Springs, Ohio was the first of two visitors to RMNP killed by lightning strike in the park last weekend. Gregory Cardwell, 52, of Scottsbluff, Nebraska, died on Saturday when another bolt struck a few hundred feet from where Teilhet died.

Neither were far off the beaten tourist path. Teilhet and Cardwell died near Rainbow Curve, a popular scenic overlook boasting parking spots and restrooms that welcome throngs of visitors as they drive Trail Ridge Road in the summer months.

In Colorado and nationwide, July is the deadliest month for lightning strikes, said Bob Glancy with the National Weather Service in Boulder. In Rocky Mountain National Park, which hosts about 3 million visitors a year, peak lightning season coincides with prime hiking and monsoon season.

Trail Ridge Road in particular can be dangerous lightning-strike country, where millions of visitors drive across the alpine tundra, above 11,000 feet, often unaccustomed to Colorado's afternoon storm cycle.

Trail Ridge Road is the highest continuous paved road in America, the only connector between the park's gateway towns of Estes Park and Granby. Eleven of the road's miles wind above treeline, with its highest point reaching 12,183 feet. In the winter the road is closed, but snow squalls can shut the road down into the summer.

It's not a good place to be caught in a lightning storm, which in Colorado can be a daily, late-summer occurrence.

"This is just one of the factors of life here in Colorado," said Glancy, a warning coordinator meteorologist for the National Weather Service in Boulder. "One of our challenges is that Rocky Mountain National Park is a beautiful place and it's high."

In that exposed and extreme terrain there is little anyone can do to escape lightning, experts say. That's something that Justin Teilhet has accepted.

"You know, it's the Rocky Mountains. It's a beautiful place," he said on Monday, a day after he returned home, relatively uninjured, to Yellow Springs. "And it was certainly no one's fault."

When people are exposed at high elevations, the best way to protect themselves is get indoors, said John Jensenius, a lightning safety specialist with the National Weather Service.

"Prior to getting into that situation, plan activities in the morning so you can avoid the threat completely," Jensenius said. "If you are outside and above treeline, quite honestly there is not a lot you can do."

Becky Teilhet died as she returned from a hike along Ute Crossing Trail. At about 1:20 p.m. Friday, lightning struck when her group was 500 feet from the trailhead at Rainbow Curve. The bolt hospitalized her husband and friend, and struck five other people, who drove themselves to Estes Park Medical Center, according to news releases from the park. All surviving strike victims were discharged over the weekend.

Cardwell died at the Rainbow Curve outlook after lightning struck just before 4 p.m. Saturday. Three other people were injured in the strike, but all were later released from the medical center in Estes Park, said spokeswoman Kerrie Hill on Monday.

Both groups were well above 10,800 feet, where the shelter of trees gives way to open alpine tundra. The weekend's deaths were the first lightning-strike fatalities in the park since 2000. On average, the state has three lightning fatalities a year, usually in July, Glancy said.

The Larimer County coroner ruled the deaths accidental, both from cardiac electromechanical interruption due to lightning strikes. If the body acts as a conductor to lightning, it channels electricity through the cardiovascular and neurological systems, which is usually fatal.

After lightning struck near Justin Teilhet, he awoke to find his friend trying to revive Becky with CPR, The Associated Press reported.

The Teilhets grew up near Yellow Springs, northeast of Dayton, where they met junior year of high school, said Justin's mother Carol Teilhet. They were getting ready to celebrate their 22 anniversary in August, and had come to the Colorado for an art show where Justin's pottery — the stuff of legend in Yellow Springs — was on display.

Teilhet returned home Sunday to a house full of people and rescue dogs, one of Becky's passions. On Monday, 80-year old Carol was lost in memories of Becky as she was 20 years ago, when the 22-year-old girl had become a cornerstone in the family.

"Becky, you know, you are the glue holding us together," Carol remembered telling her daughter-in-law.

"I'm more like epoxy," Becky countered. "It requires more than one part."

Are you afraid of lightning?

How lightning works

"Lightning is not real fancy," Glancy says. "It's electricity."

Thunderheads are like batteries, with positively-charged ice crystals that float to the top of the cloud while negatively-charged crystals sink to the bottom, Glancy said.

"Then, in response to the negative charges near the bottom of the storm, a pool of positive charges will travel along the ground below the storm," he said. "The positive charges on the ground will try to reach the storm, and the negative charges try to reach the ground. When lightning occurs, these two charges have merged."

If you're hiking in a storm and your hair starts to stand on end, that's a serious sign that charges are starting to move and that lightning is imminent.

Of course, not every situation lends itself to safe retreat inside. The next best option would be seeking shelter in a vehicle, Glancy said. Otherwise, Glancy cautions that while out in a lightning storm, people should "try not to be the tallest objects out there" — they should look for treeline, preferably thick stands of trees, when fleeing from lightning.

Some safety specialists have suggested that people crouch on their haunches, but the so-called "lightning crouch" actually makes little difference, Glancy said. True lightning safety comes back to one essential point, Glancy said: planning.

"A lot of lightning safety is being proactive, not reactive," he said.

During monsoon season in particular, climbers and hikers need to be off high mountain tops well before noon. The moment you start to see or hear storm activity you should start looking for shelter.

"If you are outside and you start to see the clouds starting to develop, it's probably a good time to start heading toward safety," said Jensenius. "Any time you can hear thunder, you should head to safety immediately."

Lightning by the numbers

Colorado has half a million lightning strikes per year, on average.

An average of three people die from lightning strikes each year in Colorado. Fifteen people are injured per year due to lightning. Most of these occur in July.

There were no lightning fatalities in 2012 and 2013 in Colorado. Severe drought years — because they have less storm activity — typically have reduced lightning fatality numbers.

In 2013, Colorado had 529,330 cloud-to-ground lightning strikes

Tips for staying safe

Ryan Haarer has these tips for what to do if you're hiking in a lightning storm. 9NEWS at 5 p.m. 07/12/14.

CHECK THE WEATHER: According to the park, a bright summer day can turn stormy within minutes, with lightning, high winds and even snow. In the Rocky Mountains, thunderstorms typically develop in the early afternoon. Elsewhere, ask rangers or check the weather service to learn about the weather patterns of the area you are visiting.

GET OUT EARLY: If hiking, start early in the day and plan to be down the mountain by noon. Summer thunderstorms can form quickly anytime in the afternoon. Get below treeline or to safe shelter before a storm strikes.

STAY ALERT: If you hear thunder, lightning is close enough to strike you. If you see lightning in the distance, it's close enough to strike you. And at altitude, if skies look threatening, a thunderstorm can develop immediately overhead. A significant lightning threat generally extends up to 10 miles from the base of a thunderstorm cloud. And on rarer occasions, bolts can strike up to 15 miles from a thunderstorm.

ABOVE TREELINE: Get inside your vehicle immediately, do not lean against the doors, and wait at least 30 minutes after a storm passes overhead. If you are away from a vehicle, get away from summits, isolated trees and rocks. Find shelter but avoid small cave entrances and rock overhangs. They won't protect you. Crouch down on your heels.

BELOW TREELINE: If you are in a forest, stay near a lower stand of trees. Stay away from tall, isolated trees or other tall objects.

WHAT'S SAFE SHELTER: Tents, trees, small caves and picnic shelters are not safe. A vehicle or a substantive, enclosed building is. Stay away from water and any metal.